Plug Valve Introduction – Types, Advantage & Applications

Plug valves are quarter-turn manual valves that use a cylindrical or tapered plug to permit or prevent straight-through flow through the body. It has a straight-through full port opening. Plug valves can use in on-off, basic moderate throttling, and diverting applications.

For plug valves, the face-to-face dimension is normally provided by ANSI Standard B16.10. However, many manufacturers have opted to use gate valve face-to-face dimensions, so that plug valves can use as a replacement for gate valves in existing processes.

Plug Valves Design

Plug valves allow for straight-through, two-way service, with the closure element located in the middle of the body. The closure element, consisting of a plug and sleeve, is accessible from the top entry in the body and is sealed with a bonnet cap. This is a diagrammatic representation of a plug valve.

The passage in the plug lines up with both the inlet and outlet ports of the valve when the plug is open. The solid part of the plug blocks the flow passage and stops fluid flow when the closure element is rotated 90° from the open position.

Many corrosive chemical services (such as hydrochloric acid, sulfuric acid, etc.) require plug valve bodies to be coated in PTFE, PVDF, PVDC, polyethylene, polypropylene, or similar materials.

Three-way plug valves are also common, with the third port being at a right angle to the inlet. As part of the three-way design, the closure element is use to divert or combine the flow.

• Diverting Flow  – The flow enters the inlet and moves through the plug, which channels the flow to one of the two outlets. When the plug is turn 90 degrees, the flow is channel to the other outlet. At the midpoint, the flow may equally divide between the two outlets.
• Combining Flow – The flow is directed from two inlets to a single outlet.

  

To maintain correct quarter-turn motion without over or under stroking of plug valves, a stop collar arrangement is use. The stop collar is design so that it fits on the top of the plug, which makes it turn with the stem of the plug.  The bonnet cap has a fixe key at a quarter-turn path. The fixe key prevents the stop collar and the plug from moving outside the quarter-turn range as the plug stem move.

Types of Plug Valves

There are various types of plug valves, as follows:

• Lubricating Plug Valve
• Non-Lubricating Plug Valve
• Multi-Port Plug Valve
• Eccentric Plug Valve
• Expanding Plug Valve

These will be discussed in detail in separate articles.

Plug Valves Applications

• Plug valves are typically use for low-pressure, low-temperature services, although there are also some high-pressure, high-temperature versions.
• Plug valves are high-capacity valves that allow directional flow control, even in moderate vacuum systems.
• Plug valves can handle gas and liquid fuel efficiently.
• The plug valves can handle extreme temperature flow, including boiler feed water, condensate, and other elements.
• Plug valves can use to regulate the flow of liquids containing suspend solids, such as slurries.

Advantages and Disadvantages of Plug Valves

Advantages

• The plug valve has a simple design with a few parts.
• Plug valves open and close easily (except for large dimensions).
• Plug valves can maintaine and repair at the place of operation.
• Plug valves have a low resistance to flow.
• Plug valves provide reliable leak-proofing.

Disadvantages

• Due to high friction, the first movement (opening-closing) requires a great deal of force.
• For NPS 4 (DN100) and larger plug valves, an actuator or gearbox is require.
• Plug valve transitions narrow flows due to conic plugs.
• Generally, plug valves are more expensive than ball valves.

Aira Euro Automation is a leading manufacturer and exporter of plug valve in India, They have a huge chain of industrial valves and Solenoid Valves.

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